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Modern Herschel wedges use a heat sink dissipate the unwanted energy. I have used one for public demonstration and mine (1¼” fitting) doesn’t get appreciably warm even after serveral hours use, although my aperture (63mm) was somewhat smaller then your 80mm. Is your Herschel wedge an 1¼”or 2″ fitting? 1¼” wedges are OK for apertures up to 100mm, whereas 2″ ones are OK up to 150mm aperture. Perhaps a 2″ one would be better for you as it will have a bigger capacity heat sink.
I find the image produced by Herschel wedges too bright for comfort so always use a post wedge filter to give me the image I want.
It looks like Alan used Dexion to construct his mounts.
Elbow telescopes were salvaged from World War II artillary guns. Back in the day amateur astronomers would use anything they could lay their hads on to observe the skies.
Although it’s been several years since I had any involvement with railway level crossings, the emergency telephones used to be lit with a beta lite.
There’s an E G Moore active in the BAA around this time, the attached image is from the second half-century Journal index. He also contributed to The Astronomer where his address was: 44 Nelson Road, Rayleigh, Essex. By the time his final Journal contribution was published (vol 92, p.47) in 1981 he had moved to 1 Hillside Villas, Station Road, Pluckley, Kent.
Attachments:
James,
The current Orwell Astronomical Society Newsletter is here
https://www.oasi.org.uk/NL/NL_202504.pdfA complete archive of previous editions is here
https://www.oasi.org.uk/NL/NL_archive.phpC/2024 (ATLAS) seems to have survived perihelion.
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Now in the national news.
I’m looking for a ‘complete solution’ rather than ‘just a battery’ and the only one I’ve seen so far was at Screwfix
As far as Ah rating is concerned the sort of observing I do is limited to public outreach work where my equipment draws about 1A and the events generally don’t last longer than six hours. So a 10Ah battery should be more than sufficient.
My ulterior motive for this is that I’m already thinking about our 2025 Autumn Weekend Meeting in Orkney and was looking at a lower weight battery than my current (17Ah, I think) lead acid jump starter/leisure battery. On the evening of Sunday September 7 there is a lunar eclipse with the Moon rising in eclipse and coming out as the evening goes on which might be worth taking a telescope for.
The Zeiss Telementor (63mm OG, 840mm focal length refractor) of the 1970’s is like this. If you screw the eyepiece holder directly into the telescope tube you won’t be able to achieve focus, either an extension tube or a diagonal is required. Zeiss manufactured six different extension tubes (in the range 20mm to 80mm, and usable singly or in multiple) to cover all circumstances.
‘Classic’ Newtonian reflectors of a few years ago had the opposite problem because the eyepiece tube couldn’t be too long as it would cut into the light path inside the main tube. (i.e. use of a diagonal was impossible.)
The Tomline Refractor at Orwell Park also suffers from poor prime focus image position (too far up the tube) which similarly makes the use of a diagonal impossible.
On the other hand a by-product of a ‘focal reducer’ or a ‘Barlow lens’ is a shift in the position of the focal plane image. The image is moved away from the objective with a Barlow and toward it with a focal reducer. This allows you to get the image plane nearer where you want it, but you have to accept a reduction or increase in magnification for any given eyepiece.
James,
Would it be possible to replace the two bevel cogs with an ordinary cog and a worm gear?
The worm would be attached to the handle and provide such mechanical disadvantage that the slit would not have enough energy to spin the handle. The downside of this arrangement would be a very great increase in the time it took to open/close the slit.
Bill.
Now looking a lot more spectacular in SoHO LASCO C3.
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The BAA Memoirs are available on SAO ADS.
https://ui.adsabs.harvard.edu/search/q=bibstem%3AMmBAA&sort=date%20asc%2C%20bibcode%20asc&p_=0
Unfortunately the person doing the scanning doesn’t seem to have worked out the pagination and sometimes the content doesn’t match the title!
Bill Barton,
Deputy Director, Historical Section.Larger than Mount Everest, apparently?
Surely the monkey is using lorgnettes (handheld spectacles)?
There was a printed index issued at our centenary in 1990. It covered volumes 51 to 100.
An index to volumes 1 to 50 was issued (in 1963!), but the print run was very short.
New refined prediction for reentry is 21 February 2024 16:31 UTC ± 5 hours.
